US4601027A - Optical FDM system - Google Patents
Optical FDM system Download PDFInfo
- Publication number
- US4601027A US4601027A US06/622,940 US62294084A US4601027A US 4601027 A US4601027 A US 4601027A US 62294084 A US62294084 A US 62294084A US 4601027 A US4601027 A US 4601027A
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- US
- United States
- Prior art keywords
- frequency
- outputs
- frequencies
- output
- oscillator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/506—Multiwavelength transmitters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/572—Wavelength control
Definitions
- This invention relates to a frequency division multiplex (FDM) system, especially for use where the transmission medium is an optical fibre cable.
- FDM frequency division multiplex
- Frequency division multiplex is well-known, and has even been proposed for use in telephone exchanges, as in British Pat. No. 455279 (STC). It is in fact often referred to as multi-channel carrier.
- An object of the invention is to provide an FDM system in which optical fibre cables are economically exploited.
- a frequency division multiplex (FDM) system in which the transmission medium is an optical fibre cable, which system provides a number of channels whose frequencies are widely and uniformly separated across the available frequency spectrum, wherein a single oscillator is associated with all of the channels and provides a single output frequency at or near to a central point of the frequency spectrum, wherein the single output frequency is applied to a modulation arrangement which generates therefrom a number of outputs each providing a carrier frequency for one of the channels, wherein the outputs are derived from the oscillator's output by the subtraction therefrom of a second frequency one or more times to give one or more further frequencies and by the addition of the second frequency to the oscillator's output to give one or more further frequencies, and wherein the further frequencies, or the further frequencies plus the original oscillator frequency are used as the carriers for the FDM channels.
- FDM frequency division multiplex
- Fig. 1 is a diagram explanatory of the frequency spectrum used
- FIG. 2 is a multiplexer/demultiplexer arrangement for an FDM system embodying the invention.
- FIG. 3 is an arrangement embodying the invention in which there is an element of switching.
- the channels to be switched are modulated with double sidebands onto carrier frequencies f 1 f 2 . . . f n and are of bandwidth Df. Between each pair of adjacent channels is an unused section of the frequency spectrum, as indicated in Equation 1.
- the local oscillator frequencies f 10 , f 20 , etc. are so allocated as to lie in these gaps above or below the signal frequencies at a frequency difference f IF therefrom. They are so chosen that
- the minimum IF gives the minimum channel spacing, and the minimum IF is 2Df, so that:
- Double side band modulation implies amplitude modulation of the light source.
- Such "Amplitude" Modulation of the guided wave is in fact a phase modulation process and for small modulation depths the double sidebands will extend many times beyond a range equal to the bandwidth of the modulating signal. This has been discussed in "Topics in Applied Physics--Integrated Optics", by J. M. Hammer (ed.T. Tamir); Vol.7, Springer-Verlag, 1982, pp 139-200.
- phase modulation process becomes in effect an amplitude modulation one, because on extinction energy is lost by radiation, reflection or deflection from the straight-through path down the waveguide.
- the spectrum of the resultant amplitude modulated signal should therefore be confined largely to a frequency range equal to plus and minus its bandwidth. Regeneration of the digital signal after the receiver will in any case remove cross-talk components.
- FIGS. 2 and 3 show arrangements based on the above discussed principles, FIG. 2 for the simpler multiplexing/demultiplexing case and FIG. 3 for a switching arrangement in which the incoming and outgoing channels do not bear a fixed relationship to each other.
- FIGS. 2 and 3 show arrangements based on the above discussed principles, FIG. 2 for the simpler multiplexing/demultiplexing case and FIG. 3 for a switching arrangement in which the incoming and outgoing channels do not bear a fixed relationship to each other.
- FIGS. 2 and 3 the transmission (multiplexing) ends are identical.
- the master oscillator output is split, with half the energy or more going to the receive end and the remainder to the transmit end.
- the transmit signal is fed into an optical splitter RNM 1 working in the Raman Nath (RN) regime, for which see the reference quoted above. Also of interest in this respect is "Interaction Between Light and Sound" by R. Adler, IEEE Spectrum, V4, No. 5, pp 42-54, May, 1967.
- This splitter RNMl also has an input via which a 500 MHz signal is applied.
- the phase excursion or the modulation index of the device RNMl is such as to make the carrier and higher order sidebands have the same amplitude.
- the carrier, the first order and second order sidebands corresponding to Bessel function J 0 , J 1 and J 2 must have roughly equal amplitudes.
- a modulation index of about 3 radians meets this criterion.
- the device RNM1 When frequency modulating the input, the device RNM1 also splits its input spacially into five outputs of frequencies f 0 , f 0 + or -f m and f 0 + or -2f m . Each of these outputs is then modulated in one of the channel modulators CM1-CM5 by one of the TV signals, and they are then combined in a combiner CB, whose output is applied to an optical fibre cable.
- Such a combiner, and also an optical splitter may be an optical star-coupler, or the equivalent thereof.
- Combination can be, as just indicated, by optical means (collimation and focussing) if the functions are on separate chips or, if they are in waveguides on the same chip, by one of the standard waveguide coupling techniques.
- the combined output is transmitted along a fibre or guide to the receive end.
- the receive end part of the master oscillators output is also transmitted along another guide or fibre to the receive end to act as the local oscillator source.
- the receive end contains a Bragg modulator device BM which shifts the local oscillator signal by an amount equal to the IF frequency, upwards in the present case.
- the signal is then split by another Raman Nath Modulator RNM2 into constituent frequencies; f 0 +f IF , f 0 +f IF + or -f m and f 0 +f IF + or -2f m .
- the information signal is split on reception by well-known means (not shown), which pass via the block marked DETECTORS--IF AMPLIFIERS, into five equal channels using a splitter SP which works on a waveguide decoupling technique. Once split these channels are respectively combined with the relevant local oscillator outputs from the device RNM2. This combination can be on the chip or directly at the photodetector. Mixing takes place in the photodetector and the resultant electrical signal is filtered and amplified to give five separate TV channels.
- each of the five local oscillator frequencies is potentially available for any channel.
- the receiver local oscillator output is split by a simple optical splitter OS into five equal parts, and each part is fed to a separate Bragg device BM1 to BM5.
- Each Bragg device can be acoustically modulated with signals at the IF frequency, at the IF frequency + or -f m , or at the IF frequency + or -2f m , as required.
- Such modulation needs several acoustic transducers only one of which is energised at any one time, and results in different Bragg angles at each frequency.
- the output is then collimated and focussed before application to the mixer. From that point on, operation is identical to the multiplexer case.
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Signal Processing (AREA)
- Optical Communication System (AREA)
Abstract
Description
f.sub.s =f.sub.n -f.sub.n-1 -2Df (1)
f.sub.(n-1)0 -f.sub.n-1 =f.sub.IF (2)
(f.sub.n -Df)-(f.sub.(n-1)0 +Df)>f.sub.IF (3)
C.sub.s =f.sub.n -f.sub.n-1 =2f.sub.IF +2Df (4)
C.sub.s =2f.sub.IF +2Df +2T +2S (5)
C.sub.Smin =4Df +2T +2S (6)
Claims (1)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8317962 | 1983-07-01 | ||
GB08317962A GB2142796B (en) | 1983-07-01 | 1983-07-01 | Optical fdm system |
Publications (1)
Publication Number | Publication Date |
---|---|
US4601027A true US4601027A (en) | 1986-07-15 |
Family
ID=10545140
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/622,940 Expired - Lifetime US4601027A (en) | 1983-07-01 | 1984-06-21 | Optical FDM system |
Country Status (8)
Country | Link |
---|---|
US (1) | US4601027A (en) |
EP (1) | EP0131818A3 (en) |
JP (1) | JPS6037847A (en) |
AU (1) | AU2987284A (en) |
CA (1) | CA1213382A (en) |
GB (1) | GB2142796B (en) |
NO (1) | NO842499L (en) |
ZA (1) | ZA844781B (en) |
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4777664A (en) * | 1985-09-30 | 1988-10-11 | U.S. Philips Corporation | Broadband optical distribution system |
US4800555A (en) * | 1987-03-03 | 1989-01-24 | American Telephone And Telegraph Company, At&T Bell Laboratories | Technique for repelling carriers in optical communications to minimize mutual interference |
US4807227A (en) * | 1986-10-15 | 1989-02-21 | Nec Corporation | Optical wavelength-division switching system with coherent optical detection system |
US4897830A (en) * | 1985-01-10 | 1990-01-30 | British Telecommunications, Public Limited Company | Optical networks |
US4910726A (en) * | 1985-01-10 | 1990-03-20 | British Telecommunications Public Limited Company | Optical fibre communication networks with local optical power feeding |
US4914648A (en) * | 1987-03-26 | 1990-04-03 | American Telephone And Telegraph Company | Multichannel, multihop lightwave communication system |
US4941208A (en) * | 1988-09-08 | 1990-07-10 | Gte Laboratories Incorporated | High performance subcarrier multiplexed optical communication system with modulation index exceeding unity |
US5010587A (en) * | 1988-03-11 | 1991-04-23 | Telefonaktiebolaget L M Ericsson | Appartaus for transmitting a coherent frequency modulated optical signal |
US5020049A (en) * | 1989-10-13 | 1991-05-28 | At&T Bell Laboratories | Optical sub-carrier multiplex television transmission system using a linear laser diode |
WO2002095991A2 (en) * | 2001-05-22 | 2002-11-28 | Opticalis Ltd. | Sub-carrier generation for optical communication |
US20050013612A1 (en) * | 2003-07-14 | 2005-01-20 | Hrl Laboratories, Llc | Multiple wavelength photonic oscillator |
US20050163171A1 (en) * | 2004-01-27 | 2005-07-28 | Hrl Laboratories, Llc | Wavelength reconfigurable laser transmitter tuned via the resonance passbands of a tunable microresonator |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4726011A (en) * | 1985-04-08 | 1988-02-16 | Itt Defense Communications, A Division Of Itt Corporation | Coherent optical fiber communication with frequency-division-multiplexing |
US4775972A (en) * | 1985-05-10 | 1988-10-04 | Itt Corporation, Defense Communications Division | Optical fiber communication for local area networks with frequency-division-multiplexing |
JPH0693666B2 (en) * | 1985-06-05 | 1994-11-16 | ソニー株式会社 | Receiver of frequency multiplex transmission system |
US4701904A (en) * | 1985-10-18 | 1987-10-20 | American Telephone And Telegraph Company, At&T Bell Laboratories | Optical local area network employing microwave modulation techniques |
EP0223258B1 (en) * | 1985-11-22 | 1994-01-26 | Nec Corporation | Wavelength division optical switching system having wavelength switching light modulators |
FR2593654B1 (en) * | 1986-01-28 | 1988-03-11 | Comp Generale Electricite | COHERENT PHOTON TELECOMMUNICATIONS DEVICE. |
US4715028A (en) * | 1986-06-13 | 1987-12-22 | Polaroid Corporation | Optical communication system |
DE3902746A1 (en) * | 1989-01-31 | 1990-08-09 | Standard Elektrik Lorenz Ag | OPTICAL BROADBAND MESSAGE TRANSMISSION SYSTEM, ESPECIALLY FOR THE SUBSCRIBER CONNECTION AREA |
DE3913520A1 (en) * | 1989-04-25 | 1990-10-31 | Standard Elektrik Lorenz Ag | OPTICAL CABLE TELEVISION TRANSMISSION SYSTEM |
US5235452A (en) * | 1989-06-02 | 1993-08-10 | Minister Of The Post Telecommunications And Space (Centre National D'etudes Des Telecommunications) | Process and switching matrix apparatus for optical transmission of signals by self-heterodyning |
FR2647987B1 (en) * | 1989-06-02 | 1994-07-22 | France Etat | METHOD FOR OPTICAL TRANSMISSION OF SIGNALS BY SELF-HETERODYNAGE AND TRANSMISSION SYSTEM WITH SWITCHING MATRIX IMPLEMENTING SUCH A METHOD |
GB2321808B (en) * | 1997-01-24 | 1999-03-17 | Plessey Telecomm | Single sideband modulators |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3845294A (en) * | 1973-05-09 | 1974-10-29 | Bell Telephone Labor Inc | Multiplexed communications system |
US4140783A (en) * | 1976-05-24 | 1979-02-20 | Smith Kline & French Laboratories Limited | Isothiazole and isoxazole sulphoxides |
US4468766A (en) * | 1982-09-30 | 1984-08-28 | The United States Of America As Represented By The Secretary Of The Navy | Optical RF downconverter |
US4530084A (en) * | 1981-10-08 | 1985-07-16 | Heinrich Hertz Institut Fuer Nachrichten Technik | Communications network with optical channels |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2436265A1 (en) * | 1974-07-27 | 1976-02-12 | Licentia Gmbh | Switching unit for telephone exchanges - connects input to output lines using at least one electron beam in C.R.T. |
-
1983
- 1983-07-01 GB GB08317962A patent/GB2142796B/en not_active Expired
-
1984
- 1984-06-21 US US06/622,940 patent/US4601027A/en not_active Expired - Lifetime
- 1984-06-21 NO NO842499A patent/NO842499L/en unknown
- 1984-06-22 ZA ZA844781A patent/ZA844781B/en unknown
- 1984-06-26 AU AU29872/84A patent/AU2987284A/en not_active Abandoned
- 1984-06-29 EP EP84107533A patent/EP0131818A3/en not_active Withdrawn
- 1984-06-29 CA CA000457820A patent/CA1213382A/en not_active Expired
- 1984-07-02 JP JP59137063A patent/JPS6037847A/en active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3845294A (en) * | 1973-05-09 | 1974-10-29 | Bell Telephone Labor Inc | Multiplexed communications system |
US4140783A (en) * | 1976-05-24 | 1979-02-20 | Smith Kline & French Laboratories Limited | Isothiazole and isoxazole sulphoxides |
US4530084A (en) * | 1981-10-08 | 1985-07-16 | Heinrich Hertz Institut Fuer Nachrichten Technik | Communications network with optical channels |
US4468766A (en) * | 1982-09-30 | 1984-08-28 | The United States Of America As Represented By The Secretary Of The Navy | Optical RF downconverter |
Non-Patent Citations (4)
Title |
---|
Griese Conference Systems Jour. of the Audio Eng. Soc., Jun. 1979, vol. 27, 6, pp. 503 506. * |
Griese--"Conference Systems"--Jour. of the Audio Eng. Soc., Jun. 1979, vol. 27, #6, pp. 503-506. |
Huber et al. Wideband F M System Applied Optics, vol. 18, 8, Apr. 15, 1979, pp. 1249 1252. * |
Huber et al.--"Wideband F-M System"--Applied Optics, vol. 18, #8, Apr. 15, 1979, pp. 1249-1252. |
Cited By (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4897830A (en) * | 1985-01-10 | 1990-01-30 | British Telecommunications, Public Limited Company | Optical networks |
US4910726A (en) * | 1985-01-10 | 1990-03-20 | British Telecommunications Public Limited Company | Optical fibre communication networks with local optical power feeding |
US4777664A (en) * | 1985-09-30 | 1988-10-11 | U.S. Philips Corporation | Broadband optical distribution system |
US4807227A (en) * | 1986-10-15 | 1989-02-21 | Nec Corporation | Optical wavelength-division switching system with coherent optical detection system |
US4800555A (en) * | 1987-03-03 | 1989-01-24 | American Telephone And Telegraph Company, At&T Bell Laboratories | Technique for repelling carriers in optical communications to minimize mutual interference |
US4914648A (en) * | 1987-03-26 | 1990-04-03 | American Telephone And Telegraph Company | Multichannel, multihop lightwave communication system |
US5010587A (en) * | 1988-03-11 | 1991-04-23 | Telefonaktiebolaget L M Ericsson | Appartaus for transmitting a coherent frequency modulated optical signal |
US4941208A (en) * | 1988-09-08 | 1990-07-10 | Gte Laboratories Incorporated | High performance subcarrier multiplexed optical communication system with modulation index exceeding unity |
US5020049A (en) * | 1989-10-13 | 1991-05-28 | At&T Bell Laboratories | Optical sub-carrier multiplex television transmission system using a linear laser diode |
WO2002095991A2 (en) * | 2001-05-22 | 2002-11-28 | Opticalis Ltd. | Sub-carrier generation for optical communication |
WO2002095991A3 (en) * | 2001-05-22 | 2004-03-04 | Opticalis Ltd | Sub-carrier generation for optical communication |
US20050013612A1 (en) * | 2003-07-14 | 2005-01-20 | Hrl Laboratories, Llc | Multiple wavelength photonic oscillator |
US7499653B2 (en) * | 2003-07-14 | 2009-03-03 | Hrl Laboratories, Llc | Multiple wavelength photonic oscillator |
US20050163171A1 (en) * | 2004-01-27 | 2005-07-28 | Hrl Laboratories, Llc | Wavelength reconfigurable laser transmitter tuned via the resonance passbands of a tunable microresonator |
US7822082B2 (en) | 2004-01-27 | 2010-10-26 | Hrl Laboratories, Llc | Wavelength reconfigurable laser transmitter tuned via the resonance passbands of a tunable microresonator |
Also Published As
Publication number | Publication date |
---|---|
GB8317962D0 (en) | 1983-08-03 |
EP0131818A2 (en) | 1985-01-23 |
GB2142796A (en) | 1985-01-23 |
EP0131818A3 (en) | 1986-06-18 |
GB2142796B (en) | 1986-07-16 |
CA1213382A (en) | 1986-10-28 |
AU2987284A (en) | 1985-01-03 |
JPS6037847A (en) | 1985-02-27 |
NO842499L (en) | 1985-01-02 |
ZA844781B (en) | 1985-03-27 |
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